The family member I am closest to is INFP and I have a pretty good friend who is ENFJ. They both frustrate me and inspire me.
The thing that frustrates me is their inability to take things at face value. In my opinion they often assume things about others and when they verbalize these things to me it's hard for me to understand where they come up with it. I want to know tangible reasons they have for assuming these things and it frustrates me to hear them say that it is just a gut feeling that they get or an intuition they experience about someone. Granted, sometimes they are right, but other times they are wrong and it causes a lot of unnecessary hurt for them and the other person involved.
Sometimes they seem to make judgements on other people and I struggle with that. Especially when that judgement is made on an assumption. And sometimes it seems like they dwell on those things and make it their responsibility to point those things out or worry over them, or sometimes to get involved to try to change that behavior in the other person.
I also struggle with their inability to be upfront with me sometimes about what they're feeling. At least this is true with the ISFP...she will show no sign of being upset with me until all of a sudden she bubbles over. I understand keeping it inside for awhile because I tend to do that, too, but it always totally catches me off guard because she didn't show ANY signs at all that it was coming.
Plus I wish with my INFP that she would commit to plans easier. I'm often in the dark about what is going to happen until the last minute and then I have to force myself to adapt and be flexible to her ideas. But this is as much to blame on my SJ'ness as her type. For either of us it requires compromise.
The idealism and unpracticality is hard for me to relate to at times.
However, I have to say that the very things that frustrate me are also things that I admire. They are things that I see as both strength and weaknesses at times, and other times things that I just simply see as differences. However, these things are all ones that I have a very hard time relating to, and often have nothing to say in response because it is just so different from how I am naturally.